rewardBeast

N=36 subjects underwent a 90-minute MRI scanning session on a GE 3T Discovery system equipped with a 32-channel head coil (Stanford Center for Cognitive and Neurobiological Imaging) using a multiband (simultaneous multi-slice) acquisition sequence (MB=8; TR=680ms; TE=30ms; flip angle=53; isotropic voxel size=2.2mm; 64 (8 by 8) axial slices with no gap). Slices were tilted approximately 30° relative to the AC–PC line to improve signal-to-noise ratio in the orbitofrontal cortex (Deichmann et al., 2003). Head padding was used to minimize head motion. All subjects have been defaced using pydeface. Sub-356's T1 anatomical contains signal outside of the brain, but no apparent mixing or distortions within the brain.

Behavioral Paradigm - the N-BackStop Task: If the current letter matched the stimulus presented N trials ago, subjects responded with one button press (target trials, 1/3 of all trials) but otherwise responded with a different button press (nontarget trials, 2/3 of all trials). The letter turned red on 1/3 of trials, which acted as a stop signal, so subjects were instructed to make neither button press. The load (i.e., N) of the N-back task was adjusted based upon error rate on no-stop trials. Subjects were instructed to remember all letters in the sequence even if they turned red. We created two Stop Signal Delay (SSD) tracking-algorithms, one for targets and another for non-targets. Each of these algorithms independently adapted to subjects’ stopping performance.

In the original analysis, for each functional scanning run, 16 discarded volumes were collected prior to the first trial to both allow for magnetic field equilibration and to collect calibration scans for the multiband reconstruction.